Instruments of the type described above are used as telephone receivers in analog and digital systems for communication. These instruments may interface with public switched telephone networks (PSTN), private branch exchanges (PBX), cellular networks, or other types of voice or data communication networks. The instrument has a number of push buttons, present as a keypad. Since such push button pads or keys not only bear the normal sequence of numbers from 0 to 9, but increasingly provided with various other functions in connection with the digitalization of the telecommunications apparatus and consequent increased functionality of the available devices, considerable enlargement of the keypad results.
It is known from VDI-Nachrichten No. 13 of Mar. 30, 1990, "The Battle is Raging with Regard to the Material", incorporated herein by reference, to provide keypads with groups of 3.times.4 or 3.times.3 buttons, in which the individual buttons are at such a distance from each other that simultaneous actuation of two buttons by the index finger appears impossible or is improbable. Such button pads, therefore, because of their layout, take up a large amount of space, which does not permit a miniaturization of the instrument. Thus, a reduction in the size of the electronic componentry of the communication instrument would not necessarily result in a smaller instrument housing due to these ergonomic constraints. Small size of mobile telecommunication instruments is particularly important because the instrument must ideally be capable of being carried with the user and placed in pockets, clothes and other constrained-size containers. Therefore, not only the electronic circuits contained within it, but also the outer dimensions of the instrument housing are to be miniaturized.